Optical metasurfaces—ultrathin layers engineered to control light through arrays of nanoscale structures—have long promised to replace bulky lenses, filters and optical components with compact, multifunctional devices. Yet turning these laboratory concepts into practical products has remained difficult. The most advanced designs typically require high-refractive-index materials, demanding nanofabrication techniques and substrates that can withstand complex processing. A new protocol published in Nature Protocols presents a route that could make metasurface production faster, more flexible and easier to scale: directly printing the optical structures from a high-index composite material called nanoparticle-embedded resin, or nanoPER.
The approach, developed by researchers including H. Kang, E. Lee and Y. Park, addresses a central challenge in nanoimprint lithography. This technique uses a patterned mould to mechanically replicate nanoscale features in a curable material, offering a less expensive and more productive alternative to conventional electron-beam lithography. However, standard imprint resins generally have relatively low refractive indices. Because metasurfaces rely on precisely manipulating the phase, amplitude and direction of light, a low-index material can reduce efficiency and limit the range of optical functions that can be achieved.
The new method incorporates high-index nanoparticles into a liquid resin before the material is cured. The resulting nanoPER combines the processing advantages of a printable polymer with the optical properties of an inorganic material. In the reported protocol, titanium dioxide nanoparticles are dispersed within the resin matrix. Titanium dioxide is widely used in photonics because it offers a high refractive index and low optical absorption in important visible and near-infrared wavelength ranges. When formulated correctly, the composite reaches an effective refractive index above 1.8 at the target wavelength, providing a stronger platform for shaping light than conventional imprint materials.
That index is crucial because the interaction between a metasurface and incoming light depends strongly on the contrast between the nanostructure and its surroundings. A higher refractive index allows nanoscale features to produce larger optical phase shifts within a smaller physical thickness. This can support more efficient wavefront control, enabling flat optical components to focus, deflect, split or otherwise transform light without relying on the curved glass elements found in traditional systems. The composite must nevertheless remain uniform and printable, since particle aggregation or excessive viscosity could introduce defects and prevent accurate replication.
The protocol describes how to formulate the TiO₂ nanoPER and use it in a single-step nanoimprint process. A patterned template transfers the desired nanostructure into the composite resin, after which the material is cured to preserve the geometry. Depending on the design, the curing step can lock features in place without requiring the multilayer deposition, alignment, etching and stripping processes associated with many top-down fabrication workflows. Reducing these steps could lower production costs while also making the fabrication sequence more accessible to laboratories that do not have extensive semiconductor-processing infrastructure.
One of the most notable advantages is substrate compatibility. Conventional metasurface fabrication often involves high temperatures, vacuum deposition or aggressive chemical treatments, which can restrict the process to rigid silicon or glass substrates. The nanoPER procedure is designed to replicate functional nanostructures on a broad range of surfaces, including flexible and curved substrates. This opens possibilities for optical components that conform to non-flat geometries, wrap around devices or integrate directly with wearable systems. Flexible metasurfaces could eventually contribute to compact sensors, portable imaging tools and optical interfaces designed for irregular surfaces.
The researchers also provide guidance for the practical variables that determine whether the process succeeds. Resin formulation affects viscosity, nanoparticle dispersion, curing behaviour and optical performance, while imprint pressure, temperature, exposure conditions and demoulding parameters influence the fidelity of the replicated features. Small deviations at the nanoscale can change how a metasurface operates, making process control essential. The protocol therefore combines materials preparation with fabrication instructions and optical characterization, allowing researchers to compare the physical structure of the printed surface with its measured response to light.
Optical characterization is especially important for confirming that the composite performs as intended. Measurements can be used to assess the refractive index, transmission, reflection and functional response of the fabricated metasurface at the target wavelength. These tests reveal whether the nanoparticle loading and curing conditions have produced the expected optical behaviour and whether the replicated pattern is sufficiently accurate. By presenting the complete workflow rather than only a demonstration device, the study aims to improve reproducibility—an important step for moving metasurfaces from individual laboratory experiments toward repeatable manufacturing.
The timing of the work reflects a broader shift in photonics. Metasurfaces are being explored for light detection and ranging, compact cameras, beam steering, optical communications and integrated photonics, but their commercial potential depends on scalable production. A printable high-index material could help bridge the gap between sophisticated optical design and manufacturable hardware. The ability to form a complete nanostructured optical layer in a single imprint step may be particularly attractive for applications that require large areas, multiple devices per batch or integration with surfaces that cannot tolerate conventional processing.
According to the authors, the full procedure can be completed within one to two days by researchers experienced in nanofabrication and optical measurements. The work does not eliminate every challenge: producing defect-free nanoparticle composites, maintaining precise feature dimensions and ensuring long-term mechanical and optical stability will remain important for real-world deployment. Even so, the TiO₂ nanoPER protocol offers a practical materials and manufacturing framework for high-index metasurfaces. By merging the optical strength of nanoparticles with the speed and versatility of polymer imprinting, it could help transform metasurfaces from highly specialized prototypes into scalable components for the next generation of compact and adaptable optical technologies.
Subject of Research: Direct printing of high-index optical metasurfaces using titanium dioxide nanoparticle-embedded resin and nanoimprint lithography.
Article Title: Direct printing of metasurfaces using formulated optical materials.
Article References: Kang, H., Lee, E., Park, Y. et al. “Direct printing of metasurfaces using formulated optical materials.” Nature Protocols (2026). https://doi.org/10.1038/s41596-026-01407-0
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41596-026-01407-0
Keywords: Optical metasurfaces, nanoimprint lithography, nanoparticle-embedded resin, nanoPER, titanium dioxide nanoparticles, high-index materials, flexible photonics, integrated photonics, nanofabrication.
